Spawning pattern of the squid Doryteuthis pleii (Blainville, 1823) (Mollusca: Cephalopoda), as a basis for understanding the species' mating system

• Grant number: 23/07751-3
• Support Opportunities: Scholarships in Brazil - Master
• Start date: December 01, 2023
• Status: Discontinued
• Field of knowledge: Biological Sciences - Zoology - Animal Behavior
• Principal Investigator: José Eduardo Amoroso Rodriguez Marian
• Grantee: Matheus Lima Silva Vieira
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 22/02746-9 - Diving in the Mesozoic Marine Revolution from the perspective of benthic and nektonic mollusks, AP.PNGP.PI
• Associated scholarship(s): 24/19926-5 - Untangling loliginid squid alternative reproductive tactics by exploring long-term sperm storage and multiple spawning, BE.EP.MS

Abstract

Cephalopods exhibit a great diversity of reproductive strategies, and understanding these attributes is crucial for comprehending the role of sexual selection in the clade's diversification. Squids from the family Loliginidae are particularly interesting in this context, as they possess a complex mating system that includes alternative reproductive tactics in males. Large males (consorts) and small males (sneakers) transfer spermatophores to distinct sites on the female's body: the oviduct opening and the buccal region, respectively. Although the consort's site is more advantageous, the sneaker's site features a seminal receptacle capable of storing sperm. Therefore, the number and interval between spawning events by the female provide essential information for understanding the reproductive success of sneakers. The species Doryteuthis pleii (Blainville, 1823) has been extensively used as a model in studies of sexual selection. However, the spawning pattern of this species remains unknown. Population biology data suggest a single reproductive event followed by death, but there are reports of females spawning more than once in captivity, as well as observations indicating no immediate post-spawning mortality. The present research proposal aims to determine the spawning pattern of D. pleii and whether this pattern could potentially confer cumulative reproductive success to the sneaker tactic due to long-term sperm storage. To achieve this goal, we will integrate: (1) histological analyses of the ovary to determine if it is synchronous (evidence of a single spawning event) or group-synchronous (more than one spawning event); (2) quantification of oocytes in the ovary and oviduct to estimate potential fecundity; (3) experimentation in captivity to analyze post-spawning females and estimate the number and time interval between spawning events; (4) determining whether sneakers' sperm stored in the seminal receptacle are used for fertilizing subsequent spawning batches of the same female.